Prior apparatuses and methods have been used for drilling underground arcuate paths under and around obstacles. Such techniques use a directional drill motor or jet bit attached to a drill string. The directional drill motor or jet bit is used to drill a path from one side of the obstacle, going under and/or around the obstacle and exiting on the opposite side of the obstacle. After the steering equipment has been removed a reamer can be attached to the drill string and pulled back or pushed through the hole to further enlarge the diameter of the hole. Reamers of consecutively larger diameters can be pushed and pulled back through the hole until a desired diameter is reached. The reamer is then attached by a swivel connected to the casing intended to be installed in the hole. The reamer is then pulled back through the hole followed by the swivel connection to the casing until the casing occupies the hole. A swivel is required to keep torque from being transmitted from the drill string and reamer to the casing.
Drilling fluid or “mud” is used to power the drill motor or jet bit and reamer and to clean the drilled hole of cuttings and stabilize the hole. Drilling fluids are generally composed of water and bentonite (high swelling clay) plus lesser amounts of special additives. The composite mixture produces a relatively viscous fluid with the capacity to entrain and carry soil and rock particles. Five to fifteen barrels per minute of mud must be pumped under sufficiently high pressure to power a typical drilling system. This fluid is pumped under pressure from the mud pump located at the surface next to the drilling rig, down through the drill pipe occupying the hole and out through the bit at the end of the drill string. Hole cutting is accomplished either by direct hydraulic jetting for soft soils or by use of a mud motor and drill bit for harder soils and rock. The fluids exit the bit in turbulent flow at the end of the borehole (face). As the fluids reverse course and move back up the annular space between the drill pipe and the borehole wall they lose velocity largely due to friction. The laminar flowing fluids carry “cuttings” (soil and rock particles) back up the annular space to the surface where they are collected and “cleaned”. The reconstituted fluids are then pumped back down the drill pipe. The drilling fluids are thus recycled as much as possible.
Horizontal drilling productivity and efficiency is directly related to maintaining constant and continuous drilling fluid “returns” along the bored path back to the entry point at the surface. An event commonly referred to as a “frac-out” occurs when excessive drilling pressure results in drilling mud escaping from the borehole and propagating toward the surface (e.g. the ground fractures and fluid escapes or propagates toward the surface). A frac-out can be costly due to work stoppage for cleanup and can severely affect environmentally sensitive areas.
A need therefore exists for apparatuses and methods for eliminating or substantially reducing these all too frequent frac-outs or inadvertent returns.